EDINBURGH, Scotland - Scottish swans may be getting killed by kindness, crippled by a diet of white bread scattered by admirers.

Experts say that the bread lacks the vitamins swans need and can lead to a disease that resembles rickets, The Scotsman reported. That can leave their limbs too weak to dive for the vitamin-rich pondweed and tadpoles that supply their normal diet.

"The birds have become reliant on white bread because that's what the public feed them," said Scott Elphinstone, an inspector with the Scottish Society for the Prevention of Cruelty to Animals.

.The SSPCA and the Royal Society for the Protection of Birds say that people who feel they must feed the swans should switch to whole-wheat bread, especially if it contains nuts and seeds, or to potatoes, carrots and similar vegetables.

The kindest course might be to give up feeding the swans completely. Bread that is not consumed can form a toxic algae bloom, and moldy bread can also poison swans.